.playground {
    position: relative;
    border: 4px solid black;
    height: 300px;
    padding: 20px;
}

.pos-box {
    /*position: static;*/
    /*position: absolute;*/
    /*left top right bottom*/
    /*!*top: 0;*!*/
    /*!*left: 0;*!*/
    /*bottom: 0;*/
    /*right: 0;*/
    position: fixed;
    top: 0;
    width: 50px;
    height: 50px;
    background: coral;
}

.navbar {
    position: fixed;
    top: 0;
    left: 0;
    right: 0;
    z-index: 2;
}
#header {
    margin-top: 60px;
}